Voice-over-Internet-Protocol (VoIP) is a set of protocols for the encoding, transporting, and routing of audio calls over Internet Protocol (IP) networks. According to VoIP, voice data may be converted into digital data and sent in packets using IP instead of the traditional circuit transmissions of the Public Switch Telephone Network (PSTN). In some VoIP systems, the analog audio stream is converted into a digital format, and may be compressed and encapsulated in IP for transport over the Internet or other types of network (e.g., local area network (LAN), wide area network (WAN), etc.) according to Real-time Transport Protocol (RTP). The converted stream is hereinafter referred to as a RTP stream.
Currently, VoIP software is available to be installed into personal computers to allow users to make VoIP calls over the personal computers. In addition to VoIP software, dedicated VoIP hardware are also available, such as VoIP telephones (also known as IP phones), VoIP gateways, VoIP conferencing, VoIP voicemail, etc. However, the typical processing power of VoIP telephones is significantly less than that of the personal computers.
Although VoIP calls are typically less expensive than the traditional telephone calls using PSTN, one obstacle in the popularization of VoIP is the lack of security. Currently, security protocols, such as Secure Real-time Transport Protocol (SRTP), are developed to provide encryption of the RTP stream in VoIP calls. However, SRTP requires the VoIP endpoints (e.g., personal computers loaded with VoIP software, VoIP telephones, VoIP gateway, VoIP conferencing, etc.) to perform the encryption and this is not possible in many cases because many VoIP endpoints are VoIP telephones with insufficient processing power to perform encryption and/or decryption. In some cases, the VoIP software installed on personal computers may not support SRTP.